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RSS2008 Vol. 32, No. 6
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2008, 32(6): 561-562,571.
[Abstract]
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Abstract:
The depolarization loss induced by heat generated in solid-state lasers was described.Then a new oscillator to compensate depolarization loss was introduced to eliminate influence on the laser output because of the depolarization.No evident change of laser shape or energy per pulse was observed along with changing repetition frequency from 20Hz to 50Hz.At 50Hz with 9.6J injection electrical energy,111.24mJ@1064nm dynamic output was obtained,the electric-optic efficiency reached 1.16% with stabilization of ±1.85%.Good compensation can be seen evidently with this new configure.
The depolarization loss induced by heat generated in solid-state lasers was described.Then a new oscillator to compensate depolarization loss was introduced to eliminate influence on the laser output because of the depolarization.No evident change of laser shape or energy per pulse was observed along with changing repetition frequency from 20Hz to 50Hz.At 50Hz with 9.6J injection electrical energy,111.24mJ@1064nm dynamic output was obtained,the electric-optic efficiency reached 1.16% with stabilization of ±1.85%.Good compensation can be seen evidently with this new configure.
2008, 32(6): 563-565.
Abstract:
To get the relation between output pulse energy and laser crystal temperature about a flash lamp pumped Cr,Tm,Ho:YAG laser with a plane-plane cavity,the temperature distribution of the laser crystal was calculated for the different cooling temperatures and pump frequencies by means of finite element method.At 15℃ and 5Hz,the maximum output pulse energy and slope efficiency were 217mJ and 1.4% respectively.However,at 10Hz,the maximum output pulse energy and slope efficiency were 56mJ and 0.9% respectively.The results show that pump threshold increases and output efficiency decreases with the increase of temperature and frequency.
To get the relation between output pulse energy and laser crystal temperature about a flash lamp pumped Cr,Tm,Ho:YAG laser with a plane-plane cavity,the temperature distribution of the laser crystal was calculated for the different cooling temperatures and pump frequencies by means of finite element method.At 15℃ and 5Hz,the maximum output pulse energy and slope efficiency were 217mJ and 1.4% respectively.However,at 10Hz,the maximum output pulse energy and slope efficiency were 56mJ and 0.9% respectively.The results show that pump threshold increases and output efficiency decreases with the increase of temperature and frequency.
2008, 32(6): 566-567,575.
Abstract:
The extinction character of sand and dust particles can cause the attenuation of visible and infrared light transmission.The optical characteristics of sand particle were calculated on the basis of the Mie theory,then the extinction coefficient was compared between sand blowing and normal weathers.The vertical optical characteristic distribution of the sand aerosol at 0.532μm,1.06μm and 10.6μm was provided according to the results measured with micro pulse lidar in Beijing.It is valuable for studying sand and dust blowing.
The extinction character of sand and dust particles can cause the attenuation of visible and infrared light transmission.The optical characteristics of sand particle were calculated on the basis of the Mie theory,then the extinction coefficient was compared between sand blowing and normal weathers.The vertical optical characteristic distribution of the sand aerosol at 0.532μm,1.06μm and 10.6μm was provided according to the results measured with micro pulse lidar in Beijing.It is valuable for studying sand and dust blowing.
2008, 32(6): 568-571.
Abstract:
In order to study the influence of dispersion on the information transfer capacity of the communication system,the mechanism of all kinds of dispersion for single-mode and multimode fibers,such as polarization mode dispersion,material dispersion,wave leading dispersion and mode dispersion,was studied by means of simulation.The expanded pulse width induced by dispersion in standard fibers whose refractive index n=1.516 and n=1.458 respectively was obtained after propagating 10km distance.The dispersion effect for multimode fibers with the propagation wavelength as 850nm and 1310nm respectively was compared.The effect of the spectrum width of the different laser sources,such as LD(Δλ=1nm) and LED(Δλ=70nm),on the pulse width was compared.It shows that the group velocity dispersion group velocity dispersion is 0 when the propagation wavelength of the system is 1.27μm for a pure silica fiber,the intra-modal dispersion becomes abnormal dispersion when the graded-index multimode fiber is in the propagation window of 850nm or 1310nm and that the expanded pulse width induced by the chromatic dispersion and modal dispersion would increase with the numerical aperture,refractive index and the spectrum width of the laser source.
In order to study the influence of dispersion on the information transfer capacity of the communication system,the mechanism of all kinds of dispersion for single-mode and multimode fibers,such as polarization mode dispersion,material dispersion,wave leading dispersion and mode dispersion,was studied by means of simulation.The expanded pulse width induced by dispersion in standard fibers whose refractive index n=1.516 and n=1.458 respectively was obtained after propagating 10km distance.The dispersion effect for multimode fibers with the propagation wavelength as 850nm and 1310nm respectively was compared.The effect of the spectrum width of the different laser sources,such as LD(Δλ=1nm) and LED(Δλ=70nm),on the pulse width was compared.It shows that the group velocity dispersion group velocity dispersion is 0 when the propagation wavelength of the system is 1.27μm for a pure silica fiber,the intra-modal dispersion becomes abnormal dispersion when the graded-index multimode fiber is in the propagation window of 850nm or 1310nm and that the expanded pulse width induced by the chromatic dispersion and modal dispersion would increase with the numerical aperture,refractive index and the spectrum width of the laser source.
2008, 32(6): 572-575.
Abstract:
This study is carried on to explore a feasible approach to transfer the irregular powder,such as Ti powder and bronze powder,into spherical powder by "balling effect".The results indicate that:(1)the balling ability of mental powder can be ranked by a balling factor K which accounts for the influence of particle size,density,special thermal property,boiling point as well as laser absorbing rate;(2)when the scanning speed vequals laser power P multiplying K,the irregular particle will be transformed into spherical powder.
This study is carried on to explore a feasible approach to transfer the irregular powder,such as Ti powder and bronze powder,into spherical powder by "balling effect".The results indicate that:(1)the balling ability of mental powder can be ranked by a balling factor K which accounts for the influence of particle size,density,special thermal property,boiling point as well as laser absorbing rate;(2)when the scanning speed vequals laser power P multiplying K,the irregular particle will be transformed into spherical powder.
2008, 32(6): 576-578,589.
Abstract:
In order to deal with the dispersion compensation in optical fiber communication systems,a dual-core dispersion compensation photonic crystal fiber(DCPCF) was put forward.The DCPCF consists of pure silicon and air,namely that the photonic crystal fiber(PCF) is tailored by changing the radius of the first and third ring.The dispersion compensation property in PCF was simulated with the plane wave expansion method and the relation between dispersion and structural parameters was studied.Simulation results show that the dispersion of this DCPCF can reach-1956.327 ps·nm-1·km-1 and also compensate the dispersion over 100 times its length of single mode fiber.DCPCF will play an important role in optical fiber communication,especially dispersion compensation.
In order to deal with the dispersion compensation in optical fiber communication systems,a dual-core dispersion compensation photonic crystal fiber(DCPCF) was put forward.The DCPCF consists of pure silicon and air,namely that the photonic crystal fiber(PCF) is tailored by changing the radius of the first and third ring.The dispersion compensation property in PCF was simulated with the plane wave expansion method and the relation between dispersion and structural parameters was studied.Simulation results show that the dispersion of this DCPCF can reach-1956.327 ps·nm-1·km-1 and also compensate the dispersion over 100 times its length of single mode fiber.DCPCF will play an important role in optical fiber communication,especially dispersion compensation.
2008, 32(6): 579-581.
Abstract:
In order to study the sensitization effect of Eu3+,Sm3+,Tb3+ and α-thienyltrifluoroacetone(TTFA) polymers,rare earth complex-doped polymers and rare earth ions complex-co doped polymers was made from the rare earth ions Eu3+,Sm3+,Tb3+ and TTFA.The fluorescence properties of these chelate complexes in ethanol were investigated.Sensitization effect properties of rare earth complex-doped polymers and rare earth ions complex-co doped polymers were found.The study results can be used in polymer optical fiber amplifiers with good development.
In order to study the sensitization effect of Eu3+,Sm3+,Tb3+ and α-thienyltrifluoroacetone(TTFA) polymers,rare earth complex-doped polymers and rare earth ions complex-co doped polymers was made from the rare earth ions Eu3+,Sm3+,Tb3+ and TTFA.The fluorescence properties of these chelate complexes in ethanol were investigated.Sensitization effect properties of rare earth complex-doped polymers and rare earth ions complex-co doped polymers were found.The study results can be used in polymer optical fiber amplifiers with good development.
2008, 32(6): 582-583,600.
Abstract:
In diode pumped Nd:YAG lasers,the quantum defect is the most important parameter determining the thermal load of the laser crystal.This can be reduced dramatically by direct pumping into the upper laser level.A bar diode stack with central wavelength of 885nm was used to pump a Nd:YAG crystal with 55mm in length and 5.5mm in diameter.Compared several output-couplers,the maximum static pulse energy of 138mJ was obtained with 58% transmittance and the corresponding optical-to-optical efficiency was 12%.The results show the possibility of 885nm diode direct pump,also it is helpful for the project's process.
In diode pumped Nd:YAG lasers,the quantum defect is the most important parameter determining the thermal load of the laser crystal.This can be reduced dramatically by direct pumping into the upper laser level.A bar diode stack with central wavelength of 885nm was used to pump a Nd:YAG crystal with 55mm in length and 5.5mm in diameter.Compared several output-couplers,the maximum static pulse energy of 138mJ was obtained with 58% transmittance and the corresponding optical-to-optical efficiency was 12%.The results show the possibility of 885nm diode direct pump,also it is helpful for the project's process.
2008, 32(6): 584-586.
Abstract:
In order to remedy the shortage of the lidar velocity azimuth display(VAD) method and improve the precision of the inversion wind velocity,a new technique was put forward with iterative pretreatment to eliminate low and oddity wind velocity and with the summation average statistical method to obtain three-dimension wind field.The wind field model was built,and then the simulation and error analysis were carried out.The results show that the absolute error of inversion wind field is within 0.5m/s,only one half of that of traditional velocity azimuth display method.
In order to remedy the shortage of the lidar velocity azimuth display(VAD) method and improve the precision of the inversion wind velocity,a new technique was put forward with iterative pretreatment to eliminate low and oddity wind velocity and with the summation average statistical method to obtain three-dimension wind field.The wind field model was built,and then the simulation and error analysis were carried out.The results show that the absolute error of inversion wind field is within 0.5m/s,only one half of that of traditional velocity azimuth display method.
2008, 32(6): 587-589.
Abstract:
The cross-phase modulation(XPM) between pulse train and continuum wave in dispersion-shifted fiber(DSF) is utilized to implement all-optical wavelength conversion.The frequency shift and broadening of continuum wave induced by XPM in DSF was experimentally observed.Then wavelength conversion was achieved through filtering by a fiber grating.The converted pulse train with repetition rate of 57.97MHz,pulse-width of 2ns and the modulation period of continuum wave of 1537nm~1560nm,almost as the same of pump pulse,was obtained.The results show that wavelength conversion based on cross-phase modulation of DSF is simple,efficient and universal with wide conversion range and high rate.
The cross-phase modulation(XPM) between pulse train and continuum wave in dispersion-shifted fiber(DSF) is utilized to implement all-optical wavelength conversion.The frequency shift and broadening of continuum wave induced by XPM in DSF was experimentally observed.Then wavelength conversion was achieved through filtering by a fiber grating.The converted pulse train with repetition rate of 57.97MHz,pulse-width of 2ns and the modulation period of continuum wave of 1537nm~1560nm,almost as the same of pump pulse,was obtained.The results show that wavelength conversion based on cross-phase modulation of DSF is simple,efficient and universal with wide conversion range and high rate.
2008, 32(6): 590-592,595.
Abstract:
In order to improve the efficiency of atmospheric signal processing of lidar,the theory of empirical mode decomposition was analyzed and the application of empirical mode decomposition in real-time processing of atmospheric echo signal was studied.The reconstruction signal after empirical mode decomposition processing is close to the signal after 100 singnals average and their correlation coefficient is 0.99 and the processing time can be decreased to 1%,which may meet the requisition of real-time processing and can restrain the interference of some thin cloud.This result will give help to real-time processing of lidar echo.
In order to improve the efficiency of atmospheric signal processing of lidar,the theory of empirical mode decomposition was analyzed and the application of empirical mode decomposition in real-time processing of atmospheric echo signal was studied.The reconstruction signal after empirical mode decomposition processing is close to the signal after 100 singnals average and their correlation coefficient is 0.99 and the processing time can be decreased to 1%,which may meet the requisition of real-time processing and can restrain the interference of some thin cloud.This result will give help to real-time processing of lidar echo.
2008, 32(6): 593-595.
Abstract:
In order to obtain the output characteristic of a frequency doubled Yb:YAG laser,a 0.1 atom fractiom doped Yb:YAG microchip crystal(4mm×1mm) end-pumped by laser diodes,and a LBO crystal were employed.With the pump power of 1.37W,frequency selected of nonlinear crystal was realized by tuning the lying angle of LBO 3.1mW TEM00 continuous wave laser at 537.8nm was obtained.The ellipticity of the output beam was 0.94.The results show that high-quality 537.8nm green laser can be obtained with intra-cavity frequency double crystal LBO and Yb:YAG laser crystals.
In order to obtain the output characteristic of a frequency doubled Yb:YAG laser,a 0.1 atom fractiom doped Yb:YAG microchip crystal(4mm×1mm) end-pumped by laser diodes,and a LBO crystal were employed.With the pump power of 1.37W,frequency selected of nonlinear crystal was realized by tuning the lying angle of LBO 3.1mW TEM00 continuous wave laser at 537.8nm was obtained.The ellipticity of the output beam was 0.94.The results show that high-quality 537.8nm green laser can be obtained with intra-cavity frequency double crystal LBO and Yb:YAG laser crystals.
2008, 32(6): 596-597,604.
Abstract:
In order to use colored calcite crystal suitably,chemical composition of lilac color calcite crystal and yellowish calcite crystal was tested with ALR 9400 X-ray fluorescence spectrometer and X-ray diffractometer respectively.Transmitted spectra of yellowish calcite crystal were measured with spectrophotometer.It is found that the yellowish calcite crystal contains trace element Mg and Sr,and the lilac color calcite crystal contains trace element Mn,Sr and Mg.Extinction ratio of colored calcite crystal polarizer can reach 10-6.The results indicate that the polarizer can be used in optical measurement systems which don't need extreme high precision.
In order to use colored calcite crystal suitably,chemical composition of lilac color calcite crystal and yellowish calcite crystal was tested with ALR 9400 X-ray fluorescence spectrometer and X-ray diffractometer respectively.Transmitted spectra of yellowish calcite crystal were measured with spectrophotometer.It is found that the yellowish calcite crystal contains trace element Mg and Sr,and the lilac color calcite crystal contains trace element Mn,Sr and Mg.Extinction ratio of colored calcite crystal polarizer can reach 10-6.The results indicate that the polarizer can be used in optical measurement systems which don't need extreme high precision.
2008, 32(6): 598-600.
Abstract:
In order to improve the third-order nonlinear optical property and the practical application of polyaniline-carbon natotube-doped polyvinyl alcohol composites were prepared by electrostatic interaction between carbon nanotubes and aniline via in situ polymerization.The third-order nonlinear properties of the samples were determined by the well-known z-scan technique at 532nm with 8ns duration,and the third-order optical nonlinear refractive indexes were calculated.Compared with pani,the third-order nonlinear properties of the samples could be improved obviously.They were prepared as film so that they could be used more widely.
In order to improve the third-order nonlinear optical property and the practical application of polyaniline-carbon natotube-doped polyvinyl alcohol composites were prepared by electrostatic interaction between carbon nanotubes and aniline via in situ polymerization.The third-order nonlinear properties of the samples were determined by the well-known z-scan technique at 532nm with 8ns duration,and the third-order optical nonlinear refractive indexes were calculated.Compared with pani,the third-order nonlinear properties of the samples could be improved obviously.They were prepared as film so that they could be used more widely.
2008, 32(6): 601-604.
Abstract:
In order to study the performance of YAG-MIG(metallic inert gas)arc hybrid welding joint of ZL-114A aluminum alloy,the tensile test and scanning electronic microscope were adopted to analyze the mechanical properties and microstructure of welded joint.The microstructure of the bead was smaller than that of base metal because of the inherent splat cooling of welding and the beneficial effect of titanium(Ti),and the microstructure was smaller when the heat input was smaller.The crystal of heat affected zone(HAZ) was coursing,and had a softened zone near the bond line because of the precipitation and dissolution of the solid solution phase in base metal.The softened zone was the worst mechanics in the joint,which in the YAG-MIG hybrid welding was usually much narrower than that in the single MIG welding.The tensile-strength of the YAG-MIG hybrid welding joint was up to 80% of the base metal,In order to study the performance of YAG-MIG(metallic inert gas)arc hybrid welding joint of ZL-114A aluminum alloy,the tensile test and scanning electronic microscope were adopted to analyze the mechanical properties and microstructure of welded joint.The microstructure of the bead was smaller than that of base metal because of the inherent splat cooling of welding and the beneficial effect of titanium(Ti),and the microstructure was smaller when the heat input was smaller.The crystal of heat affected zone(HAZ) was coursing,and had a softened zone near the bond line because of the precipitation and dissolution of the solid solution phase in base metal.The softened zone was the worst mechanics in the joint,which in the YAG-MIG hybrid welding was usually much narrower than that in the single MIG welding.The tensile-strength of the YAG-MIG hybrid welding joint was up to 80% of the base metal,the fracture characteristic belonged to brittle fracture.The results show that the high quality joint can be achieved in a high welding speed when the welding parameter is appropriate,so the YAG-MIG hybrid welding is an ideal welding technique for aluminum alloy with high efficiency.the fracture characteristic belonged to brittle fracture.The results show that the high quality joint can be achieved in a high welding speed when the welding parameter is appropriate,so the YAG-MIG hybrid welding is an ideal welding technique for aluminum alloy with high efficiency.
In order to study the performance of YAG-MIG(metallic inert gas)arc hybrid welding joint of ZL-114A aluminum alloy,the tensile test and scanning electronic microscope were adopted to analyze the mechanical properties and microstructure of welded joint.The microstructure of the bead was smaller than that of base metal because of the inherent splat cooling of welding and the beneficial effect of titanium(Ti),and the microstructure was smaller when the heat input was smaller.The crystal of heat affected zone(HAZ) was coursing,and had a softened zone near the bond line because of the precipitation and dissolution of the solid solution phase in base metal.The softened zone was the worst mechanics in the joint,which in the YAG-MIG hybrid welding was usually much narrower than that in the single MIG welding.The tensile-strength of the YAG-MIG hybrid welding joint was up to 80% of the base metal,In order to study the performance of YAG-MIG(metallic inert gas)arc hybrid welding joint of ZL-114A aluminum alloy,the tensile test and scanning electronic microscope were adopted to analyze the mechanical properties and microstructure of welded joint.The microstructure of the bead was smaller than that of base metal because of the inherent splat cooling of welding and the beneficial effect of titanium(Ti),and the microstructure was smaller when the heat input was smaller.The crystal of heat affected zone(HAZ) was coursing,and had a softened zone near the bond line because of the precipitation and dissolution of the solid solution phase in base metal.The softened zone was the worst mechanics in the joint,which in the YAG-MIG hybrid welding was usually much narrower than that in the single MIG welding.The tensile-strength of the YAG-MIG hybrid welding joint was up to 80% of the base metal,the fracture characteristic belonged to brittle fracture.The results show that the high quality joint can be achieved in a high welding speed when the welding parameter is appropriate,so the YAG-MIG hybrid welding is an ideal welding technique for aluminum alloy with high efficiency.the fracture characteristic belonged to brittle fracture.The results show that the high quality joint can be achieved in a high welding speed when the welding parameter is appropriate,so the YAG-MIG hybrid welding is an ideal welding technique for aluminum alloy with high efficiency.
2008, 32(6): 605-607.
Abstract:
In order to obtain excellent optoelectronic integrated device and optical waveguide,it is significant to study the preparation and attribute of nano-porous oxidized silicon.Porous silicon samples were prepared by electrochemical anodic oxidization.After oxidization at high temperature,nano-porous oxidized silicon samples was fabricated.The samples of porous silicon and nano-porous oxidized silicon were detected with photoluminescence and Fourier transform infrared spectroscopy.The test results demonstrated that compared with porous silicon,the photoluminescence(PL) peak of porous oxidized silicon shifted to a shorter wavelength,i.e.so called "blue shift",along with obvious reduction of PL intensity.The surface of porous silicon was saturated by hydrogen,however,the most of Si—H bonds on the surface of nano-porous silicon were replaced by Si—O bonds after oxidization.The peak blue shift was induced by quantum confinement effect.The reduction of PL intensity was induced by the reduction of radioactive recombination center on the nano-crystalline surface and the diminution of nano-crystalline Si column's size.
In order to obtain excellent optoelectronic integrated device and optical waveguide,it is significant to study the preparation and attribute of nano-porous oxidized silicon.Porous silicon samples were prepared by electrochemical anodic oxidization.After oxidization at high temperature,nano-porous oxidized silicon samples was fabricated.The samples of porous silicon and nano-porous oxidized silicon were detected with photoluminescence and Fourier transform infrared spectroscopy.The test results demonstrated that compared with porous silicon,the photoluminescence(PL) peak of porous oxidized silicon shifted to a shorter wavelength,i.e.so called "blue shift",along with obvious reduction of PL intensity.The surface of porous silicon was saturated by hydrogen,however,the most of Si—H bonds on the surface of nano-porous silicon were replaced by Si—O bonds after oxidization.The peak blue shift was induced by quantum confinement effect.The reduction of PL intensity was induced by the reduction of radioactive recombination center on the nano-crystalline surface and the diminution of nano-crystalline Si column's size.
2008, 32(6): 608-610.
Abstract:
In order to decrease the temperature gradient between sample and substrate,reduce and suppress the thermal stress,improve the quality of sample forming,a substrate preheating system for laser metal deposition shaping(LMDS) is developed.It consists of substrates preheater,intelligent proportion-integral-derivation controller and computer serial collecting and feedback control components.Using the self-developed LMDS system and substrate preheating system,the actual experiments are conducted.Experimental results show that substrate preheating can significantly improve the quality of the sample and reduce the thermal stress during shaping process.
In order to decrease the temperature gradient between sample and substrate,reduce and suppress the thermal stress,improve the quality of sample forming,a substrate preheating system for laser metal deposition shaping(LMDS) is developed.It consists of substrates preheater,intelligent proportion-integral-derivation controller and computer serial collecting and feedback control components.Using the self-developed LMDS system and substrate preheating system,the actual experiments are conducted.Experimental results show that substrate preheating can significantly improve the quality of the sample and reduce the thermal stress during shaping process.
2008, 32(6): 611-613,638.
Abstract:
Lidar multiple scattering return from clouds was simulated by means of semianalytic Monte Carlo method in order to obtain atmosphere extinction and backscattering coefficeint exactly.The influence of the receiver field of view and medium optical depth on multiple scattering was discussed.The relation between cirrus/water clouds of multiple scattering factor and optical depth was studied.The results show that the presence of the multiple scattering can lead to an underestimation of the extinction coefficient and has little influence on backscattering coefficient.
Lidar multiple scattering return from clouds was simulated by means of semianalytic Monte Carlo method in order to obtain atmosphere extinction and backscattering coefficeint exactly.The influence of the receiver field of view and medium optical depth on multiple scattering was discussed.The relation between cirrus/water clouds of multiple scattering factor and optical depth was studied.The results show that the presence of the multiple scattering can lead to an underestimation of the extinction coefficient and has little influence on backscattering coefficient.
2008, 32(6): 614-617.
Abstract:
In order to study the effect of the technical parameters of a spaceborne atmosphere sounding lidar on its aerosol detectability,atmosphere backscattering returned signals and signal-to-noise ratio of sounding signal were numerically analyzed by making use of appropriate atmosphere pattern and setting parameters of a spaceborne atmosphere sounding lidar.The detectability of a spaceborne atmosphere sounding lidar about dust and cirruswas simulated.The simulation results revealed that a spaceborne atmosphere sounding lidar's horizontal resolution setting for aerosol detection should be 75km,and its sounding ability for detecting aerosol could achieve the detection requirement at night only and that the horizontal resolution for cirrus and dust detection should be 7.5km.The obtained results offer academic foundation of parameters,setting for manufacture of a spaceborne atmosphere sounding lidar.
In order to study the effect of the technical parameters of a spaceborne atmosphere sounding lidar on its aerosol detectability,atmosphere backscattering returned signals and signal-to-noise ratio of sounding signal were numerically analyzed by making use of appropriate atmosphere pattern and setting parameters of a spaceborne atmosphere sounding lidar.The detectability of a spaceborne atmosphere sounding lidar about dust and cirruswas simulated.The simulation results revealed that a spaceborne atmosphere sounding lidar's horizontal resolution setting for aerosol detection should be 75km,and its sounding ability for detecting aerosol could achieve the detection requirement at night only and that the horizontal resolution for cirrus and dust detection should be 7.5km.The obtained results offer academic foundation of parameters,setting for manufacture of a spaceborne atmosphere sounding lidar.
2008, 32(6): 618-620,627.
Abstract:
In order to study the mechanism of metal deposition from aqueous solution induced by low power CO2 laser irradiation,dynamic force microscope(DFM) was used to analyze the crystallite distribution and it's growth of Ag deposition.Electronic probe micro-analysis(EPMA) was adopted to analyze the metal deposition on the epoxy surface along the transverse and longitude directions,and X-ray diffraction(XRD) was used to analyze the crystal growth of Ag-Cu deposited by electroless-plating.Ag crystallites distribution and its growth varied with the technical parameters.The transverse deposition on the epoxy surface defined the width of metal deposition and the longitude deposition defined its thickness.Although the crystal lattice parameters of Cu deposited on Ag by electroless-plating changed little,the crystallites grew in direction of (111),(200) and (220) of crystal,because the impurity atom penetrated in the Cu layer in the deposition process.
In order to study the mechanism of metal deposition from aqueous solution induced by low power CO2 laser irradiation,dynamic force microscope(DFM) was used to analyze the crystallite distribution and it's growth of Ag deposition.Electronic probe micro-analysis(EPMA) was adopted to analyze the metal deposition on the epoxy surface along the transverse and longitude directions,and X-ray diffraction(XRD) was used to analyze the crystal growth of Ag-Cu deposited by electroless-plating.Ag crystallites distribution and its growth varied with the technical parameters.The transverse deposition on the epoxy surface defined the width of metal deposition and the longitude deposition defined its thickness.Although the crystal lattice parameters of Cu deposited on Ag by electroless-plating changed little,the crystallites grew in direction of (111),(200) and (220) of crystal,because the impurity atom penetrated in the Cu layer in the deposition process.
2008, 32(6): 621-623.
Abstract:
In order to achieve single random phase encoding of color images,based on the principle of random phase encoding and multi-wavelength technology,the random phase encoding of trichromatic images was realized.Theoretical analysis and digital simulation results show that using spotlight illumination systems to realize random phase encoding of color images is feasible.As the installations are reduced,the light energy losses and the corresponding image noise from random phase mask is effectively reduced.
In order to achieve single random phase encoding of color images,based on the principle of random phase encoding and multi-wavelength technology,the random phase encoding of trichromatic images was realized.Theoretical analysis and digital simulation results show that using spotlight illumination systems to realize random phase encoding of color images is feasible.As the installations are reduced,the light energy losses and the corresponding image noise from random phase mask is effectively reduced.
2008, 32(6): 624-627.
Abstract:
The influence of surface roughness on laser absorptivity was studied to better control the temperature of workpiece during laser heat treatment process and supply more precise calculate model of laser absorptivity for mathematical simulation.The surface outline of material was equivalent treated,then mathematical model was set up.The laser aborptivity was measured by lumped parameter method,which was agreed with the value of laser absorptivity calculated by theoretical formula.The results indicated that the mathematical model could exactly describe the influence of surface roughness on laser absorptivity.
The influence of surface roughness on laser absorptivity was studied to better control the temperature of workpiece during laser heat treatment process and supply more precise calculate model of laser absorptivity for mathematical simulation.The surface outline of material was equivalent treated,then mathematical model was set up.The laser aborptivity was measured by lumped parameter method,which was agreed with the value of laser absorptivity calculated by theoretical formula.The results indicated that the mathematical model could exactly describe the influence of surface roughness on laser absorptivity.
2008, 32(6): 628-630,634.
Abstract:
The photo detector is an important device,which affects the detection capability in laser altimeters.In order to maintain the detector's best performance,an approximation algorithm was developed in which the approximate distribution function was used to simulate the output of the detector,so that the relationship among false detect probability,threshold and detector's gain was obtained,and the best combination of the three parameters were found.The experiment results indicate that the detector's receiver circuit based on the approximation algorithm owns apparent improvement in detect probability and echo signal-to-noise.This result is benefit for analyzing the object characteristics of laser altimeter and rebuilding the three-dimension contour of terrain and physiognomy.
The photo detector is an important device,which affects the detection capability in laser altimeters.In order to maintain the detector's best performance,an approximation algorithm was developed in which the approximate distribution function was used to simulate the output of the detector,so that the relationship among false detect probability,threshold and detector's gain was obtained,and the best combination of the three parameters were found.The experiment results indicate that the detector's receiver circuit based on the approximation algorithm owns apparent improvement in detect probability and echo signal-to-noise.This result is benefit for analyzing the object characteristics of laser altimeter and rebuilding the three-dimension contour of terrain and physiognomy.
2008, 32(6): 631-634.
Abstract:
The passively mode-locked of nonlinear amplifying loop mirror(NALM) configuration is used to study the influence of mode-locked pulse induced by the nonlinear effect of optical fiber.After analyzing the transmission characteristic theory of nonlinear amplifying loop mirror,experiments were executed for a passively mode-locked erbium-doped fiber laser.It was found that the steady mode-locked pulse phenomenon with repeat frequency of 280.2MHz,center wavelength of 1556.235nm and line width of 0.4nm.The study is helpful for thorough understanding the passively mode-locked phenomenon and follow-up research.
The passively mode-locked of nonlinear amplifying loop mirror(NALM) configuration is used to study the influence of mode-locked pulse induced by the nonlinear effect of optical fiber.After analyzing the transmission characteristic theory of nonlinear amplifying loop mirror,experiments were executed for a passively mode-locked erbium-doped fiber laser.It was found that the steady mode-locked pulse phenomenon with repeat frequency of 280.2MHz,center wavelength of 1556.235nm and line width of 0.4nm.The study is helpful for thorough understanding the passively mode-locked phenomenon and follow-up research.
2008, 32(6): 635-638.
Abstract:
An close-loop real-time algorithm of improvement singular value decomposition(SVD) modal reconstruction of wavefront was introduced in order to solve the optimal control voltages of adaptive optics based on the micromachined membrane deformable mirror(MMDM) and reduce the incident wavefront aberration to the minimum.By adjusting the control parameters such as g1,gθ and W,reconstruction precision and convergence speed of wavefront were optimized.Wavefront aberration from the human eye was introduced as the incident wavefront of adaptive optics,and the reconstruction precision and convergence speed were improved by comparing the existent algorithms of wavefront reconstruction.As a result,the close-loop real-time algorithm of the improved SVD to some extent settled the control voltages of MMDM,which has the characteristic of great intercourse membrane and monotony but nonlinear driving electrode.This algorithm has good application and flexibility.
An close-loop real-time algorithm of improvement singular value decomposition(SVD) modal reconstruction of wavefront was introduced in order to solve the optimal control voltages of adaptive optics based on the micromachined membrane deformable mirror(MMDM) and reduce the incident wavefront aberration to the minimum.By adjusting the control parameters such as g1,gθ and W,reconstruction precision and convergence speed of wavefront were optimized.Wavefront aberration from the human eye was introduced as the incident wavefront of adaptive optics,and the reconstruction precision and convergence speed were improved by comparing the existent algorithms of wavefront reconstruction.As a result,the close-loop real-time algorithm of the improved SVD to some extent settled the control voltages of MMDM,which has the characteristic of great intercourse membrane and monotony but nonlinear driving electrode.This algorithm has good application and flexibility.
2008, 32(6): 639-641,662.
Abstract:
In order to study the frequency up-conversion in single model double cladding Er3+-Yb3+co-doped fiber,the green fluorescence emitted by single model double cladding Er3+-Yb3+co-doped fiber was measured with a fluorphotometer and compared with the green fluorescence in Yb3+ doped fiber.The results show that the fluorescence in the single model double cladding Er3+-Yb3+ co-doped fiber is attributed to the absorption of Er3+ ions in the excited state of and the Yb3+ ions only transfer the pump energy to the Er3+ ions.It leads to the difference of emissive fluorescence between the double cladding Er3+-Yb3+co-doped fiber and Yb3+ doped fiber in the spectra and the power and its variation law.
In order to study the frequency up-conversion in single model double cladding Er3+-Yb3+co-doped fiber,the green fluorescence emitted by single model double cladding Er3+-Yb3+co-doped fiber was measured with a fluorphotometer and compared with the green fluorescence in Yb3+ doped fiber.The results show that the fluorescence in the single model double cladding Er3+-Yb3+ co-doped fiber is attributed to the absorption of Er3+ ions in the excited state of and the Yb3+ ions only transfer the pump energy to the Er3+ ions.It leads to the difference of emissive fluorescence between the double cladding Er3+-Yb3+co-doped fiber and Yb3+ doped fiber in the spectra and the power and its variation law.
2008, 32(6): 642-644,658.
Abstract:
In order to study the thermal effect of Nd:GdVO4 crystal pumped by variable radius LD bar in a resonator fiber,the theoretical values and experiment values were compared and they're largely in accord with those based on the new physics model with variable Gaussian radius.The results showed that the maximum temperature rise of 199.545℃ and the maximum thermal distortion of 1.33μm could be obtained in the center of the pump end surface when the Nd:GdVO4 laser crystal was pumped by a laser diode with an output power of 15W from the center of end face.This new method can be applied in the research of the other thermal problems of laser crystal and offer theoretical basis for solving the thermal problems in laser system effectively.
In order to study the thermal effect of Nd:GdVO4 crystal pumped by variable radius LD bar in a resonator fiber,the theoretical values and experiment values were compared and they're largely in accord with those based on the new physics model with variable Gaussian radius.The results showed that the maximum temperature rise of 199.545℃ and the maximum thermal distortion of 1.33μm could be obtained in the center of the pump end surface when the Nd:GdVO4 laser crystal was pumped by a laser diode with an output power of 15W from the center of end face.This new method can be applied in the research of the other thermal problems of laser crystal and offer theoretical basis for solving the thermal problems in laser system effectively.
2008, 32(6): 645-647,666.
Abstract:
In order to obtain the single-mode output of a diode laser in 795nm,a system of anti-reflection-coated frequency-tuning diode laser with grating-feedback extended-cavity was presented.Experiments were executed in the laser.It works in 795nm with a mode-hop-free continuous scanning range of roughly 7.6GHz.The result shows,the output linewidth is about 2.5MHz and the output power can achieve more than 43mW with a 110mA injection current.The diode laser can be very useful in the research of atomic coherent effect when laser interacts with Rb atoms.
In order to obtain the single-mode output of a diode laser in 795nm,a system of anti-reflection-coated frequency-tuning diode laser with grating-feedback extended-cavity was presented.Experiments were executed in the laser.It works in 795nm with a mode-hop-free continuous scanning range of roughly 7.6GHz.The result shows,the output linewidth is about 2.5MHz and the output power can achieve more than 43mW with a 110mA injection current.The diode laser can be very useful in the research of atomic coherent effect when laser interacts with Rb atoms.
2008, 32(6): 648-650,654.
Abstract:
In order to study the relationship between the contrast of holographic grating and the root mean square(RMS) value of interferential fringe moving,a fringe locking system constituted by Moire fringe theory and charge coupled device camera is used to shot holographic grating.The value of moving Moire fringe is real-time gathered by CCD.It has been discovered that the fringe moving is composed by slowly excursion and vibration of 3.1Hz.And the RMS value of fringe moving is correlated with the contrast of holographic grating.Academic reference is put forward for testing weather the quality of holographic grating is eligible or not.The results showed that the RMS value should be less than 0.05λ to improve the quality of grating.And the fringe locking system can choke back the slowly fringe moving.
In order to study the relationship between the contrast of holographic grating and the root mean square(RMS) value of interferential fringe moving,a fringe locking system constituted by Moire fringe theory and charge coupled device camera is used to shot holographic grating.The value of moving Moire fringe is real-time gathered by CCD.It has been discovered that the fringe moving is composed by slowly excursion and vibration of 3.1Hz.And the RMS value of fringe moving is correlated with the contrast of holographic grating.Academic reference is put forward for testing weather the quality of holographic grating is eligible or not.The results showed that the RMS value should be less than 0.05λ to improve the quality of grating.And the fringe locking system can choke back the slowly fringe moving.
2008, 32(6): 651-654.
Abstract:
Because it is impossible to use the matrix method and Runge-Kutta method to acquire the dynamic response of fiber Bragg grating(FBG) when analyzing the reflection spectrum and time-delay characteristic of FBG,it is proposed to compute the dynamical response characteristic of FBG with respect to the input of continual wave(CW) and Gaussian pulse,by means of coordinate transformation combined with finite difference method.The acquired reflectivity under conditions of the input of CW keeps in accord with that acquired by the Runge-Kutta method,which proves the validity of this method.
Because it is impossible to use the matrix method and Runge-Kutta method to acquire the dynamic response of fiber Bragg grating(FBG) when analyzing the reflection spectrum and time-delay characteristic of FBG,it is proposed to compute the dynamical response characteristic of FBG with respect to the input of continual wave(CW) and Gaussian pulse,by means of coordinate transformation combined with finite difference method.The acquired reflectivity under conditions of the input of CW keeps in accord with that acquired by the Runge-Kutta method,which proves the validity of this method.
2008, 32(6): 655-658.
Abstract:
In order to study the compensation effect of the polarization mode dispersion(PMD) when the degree of polarization and electrical power are employed as feedback signals in a fibre-optic communication system,the performance between two feedback signals are compared by means of numerical simulation.The simulation results show that when high order PMD is not considered,two signals are linearly changed with differential group delay(DGD).But when the high order PMD is considered,two signals are not linearly correlative with DGD.On the other hand,the performance of degree of polarization is better than that of electrical power.These results will be useful for adaptive PMD compensation.
In order to study the compensation effect of the polarization mode dispersion(PMD) when the degree of polarization and electrical power are employed as feedback signals in a fibre-optic communication system,the performance between two feedback signals are compared by means of numerical simulation.The simulation results show that when high order PMD is not considered,two signals are linearly changed with differential group delay(DGD).But when the high order PMD is considered,two signals are not linearly correlative with DGD.On the other hand,the performance of degree of polarization is better than that of electrical power.These results will be useful for adaptive PMD compensation.
2008, 32(6): 659-662.
Abstract:
In order to increase the transmission distance for optical millimeter wave over an optical fiber,a novel scheme for optical millimeter wave generation with optical carrier suppression(OCS) modulation by external modulator in a radio over fiber(ROF) system was proposed.At the central station,a CW wave was intensity modulated by the RF signal to generate OCS signal.After the pure optical carrier was filtered,an optical interleaver was employed to separate the spectrum of the upper sideband and the lower sideband of the generated OCS signal.After the lower sideband signal was modulated with a baseband data at 2.5Gbit/s,it was recombined with the unmodulated signal to generate optical mm-wave,and then transmitted to the base station over a single mode fiber(SMF).In the base station,the electrical mm-wave signal was generated by optical electrical(O/E) conversion.The dispersion performance of the generated mm-wave was theoretically analyzed.The optical millimeter wave could be transmitted 40km over a single mode fiber in the experiment.The simulation and experiment results show that it can immune the fading effect and increase the transmission distance for optical millimeter wave over fibers with this method.
In order to increase the transmission distance for optical millimeter wave over an optical fiber,a novel scheme for optical millimeter wave generation with optical carrier suppression(OCS) modulation by external modulator in a radio over fiber(ROF) system was proposed.At the central station,a CW wave was intensity modulated by the RF signal to generate OCS signal.After the pure optical carrier was filtered,an optical interleaver was employed to separate the spectrum of the upper sideband and the lower sideband of the generated OCS signal.After the lower sideband signal was modulated with a baseband data at 2.5Gbit/s,it was recombined with the unmodulated signal to generate optical mm-wave,and then transmitted to the base station over a single mode fiber(SMF).In the base station,the electrical mm-wave signal was generated by optical electrical(O/E) conversion.The dispersion performance of the generated mm-wave was theoretically analyzed.The optical millimeter wave could be transmitted 40km over a single mode fiber in the experiment.The simulation and experiment results show that it can immune the fading effect and increase the transmission distance for optical millimeter wave over fibers with this method.
2008, 32(6): 663-666.
Abstract:
In order to study the focusing properties of cosine-squared Gaussian beams(CsSGB) through a lens without aperture,the equation for the axial irradiance distribution of focused CsSGB are derived based on the Collins formula,and the analytical expression of beams waist width is presented using the second-order moment method.The double focal switch of axial intensity and the focal shift of focal plane where the real position of beams waist located are studied with numerical method.The dependence of both effects discussed above on the beams parameter b,relative incident separation s' and beams Fresnel number NF are analyzed.Results show that double focal switch can take place only for b1,and the real focal plane has a shift if s'≠1.
In order to study the focusing properties of cosine-squared Gaussian beams(CsSGB) through a lens without aperture,the equation for the axial irradiance distribution of focused CsSGB are derived based on the Collins formula,and the analytical expression of beams waist width is presented using the second-order moment method.The double focal switch of axial intensity and the focal shift of focal plane where the real position of beams waist located are studied with numerical method.The dependence of both effects discussed above on the beams parameter b,relative incident separation s' and beams Fresnel number NF are analyzed.Results show that double focal switch can take place only for b1,and the real focal plane has a shift if s'≠1.
2008, 32(6): 667-669,672.
Abstract:
In order to improve the measuring accuracy of aerosol wavelength exponent measured by Raman-Mie lidar(RML),the uncertainty propagation formula was used to analyze the uncertainty in detail.The uncertainties of signal,transmission ratio and assumed scattering ratio Rc were calculated based on the data measured over the west suburb of the city of Hefei.Commonly,below 6km,assuming the relative uncertainty of reference value of the scattering ratio Rc was dfined by the difference between the reference and real valves,the uncertainty of the signal and the transmission ratio was less than 30% and 4% respectively.The analytical results showed that the uncertainty of aerosol wavelength exponent could be reduced by increasing pulsed laser energy,prolonging signal collecting time and more accurately demarcating assumed Rc.
In order to improve the measuring accuracy of aerosol wavelength exponent measured by Raman-Mie lidar(RML),the uncertainty propagation formula was used to analyze the uncertainty in detail.The uncertainties of signal,transmission ratio and assumed scattering ratio Rc were calculated based on the data measured over the west suburb of the city of Hefei.Commonly,below 6km,assuming the relative uncertainty of reference value of the scattering ratio Rc was dfined by the difference between the reference and real valves,the uncertainty of the signal and the transmission ratio was less than 30% and 4% respectively.The analytical results showed that the uncertainty of aerosol wavelength exponent could be reduced by increasing pulsed laser energy,prolonging signal collecting time and more accurately demarcating assumed Rc.
2008, 32(6): 670-672.
Abstract:
The laser inspection system was applied to measure the focus location of laser facula on the target.The measurement principle was analysed in order to test the measurement precision of the laser inspection system and the laser standard simulation target was applied in the test.According to the measurement principle of the system,the test principle and method of the laser standard simulation target was elaborated.Considering the testing method and results in measuring the brim echo rate of the laser standard simulation target,the measurement error model was established and the measurement precision was estimated under the statistic method and error theory.The laser standard simulation target was successfully used in the check and acception of the laser inspection system.The conclusion made from the test result is that the laser standard simulation target is of high accuracy and the test method is economically and operationally excellent.
The laser inspection system was applied to measure the focus location of laser facula on the target.The measurement principle was analysed in order to test the measurement precision of the laser inspection system and the laser standard simulation target was applied in the test.According to the measurement principle of the system,the test principle and method of the laser standard simulation target was elaborated.Considering the testing method and results in measuring the brim echo rate of the laser standard simulation target,the measurement error model was established and the measurement precision was estimated under the statistic method and error theory.The laser standard simulation target was successfully used in the check and acception of the laser inspection system.The conclusion made from the test result is that the laser standard simulation target is of high accuracy and the test method is economically and operationally excellent.
